Polyisocyanates as coating components for coating means rich in solids

Abstract

A description is given of polyisocyanates of the formula Iin whichR and R' are identical or different and are alkyl groups having 1-4 carbon atoms andn is on average from 1.5 to 5and also of a process for preparing these polyisocyanates in which a polyamine of the formula IIin which R, R', and n are as defined above, is reacted with phosgene. The new polyisocyanates are suitable for producing crosslinked polyurethanes from reaction mixtures with low solvent content and for producing coating compositions or adhesives. Also described are the coating compositions and adhesives, and their use.

What is claimed is:  
     
       1. A polyisocyanate of the formula I                    
       in which 
       R and R′ are identical or different and are alkyl groups having 1-4, carbon atoms and  
       n is on average from 1.5 to 5.  
     
     
       2. A polyisocyanate as claimed in  claim 1 , characterized in that it consists of a mixture of homologs with n=1 to n=10. 
     
     
       3. A polyisocyanate as claimed in  claim 1 , characterized in that it has a viscosity of below 400 mPas. 
     
     
       4. A process for preparing polyisocyanates of the formula I                    
       in which 
       R and R′ are identical or different alkyl groups having 1-4 carbon atoms and  
       n is on average from 1.5 to 5,  
       characterized in that a polyamine of the formula II                    
       in which R, R′ and n are as defined above is reacted with phosgene. 
     
     
       5. A coating composition or adhesive comprising 
       a) polyisocyanates of the formula I as defined in 1, it being possible for the polyisocyanates to be in blocked form, as crosslinkers.  
       b) if desired, further crosslinkers, and  
       c) isocyanate-reactive polymers, oligomers and/or low molecular mass compounds, as binders.  
     
     
       6. A coating composition or adhesive as claimed in  claim 5 , characterized in that the fraction of the polyisocyanates of formula I in the overall crosslinker amount is from 5% by weight to 100% by weight. 
     
     
       7. A coating composition or adhesive as claimed in  claim 5 , characterized in that the further crosslinkers comprise blocked at nonblocked further polyisocyanate. 
     
     
       8. A coating composition or adhesive as claimed in  claim 5  characterized in that the binder comprises hydroxy-functional polymers, oligomers and/or low molecular mass compounds. 
     
     
       9. A coating composition or adhesive as claimed in  claim 8 , characterized in that the binders are selected from the group consisting of hydroxy-functional polyacrylates, polyesters, polyurethanes, acrylated polyurethanes, acrylated polyesters, polylactones, polycarbonates, polyethers, (meth)acrylatediols, and C 9 -C 14  alkanepolyols.